Flat gaskets for use in internal combustion engines are known. Such gaskets generally have an inner load-bearing core and a layer of elastomeric material on both sides of the core to improve the seal. Flat gaskets of this type include cylinder-head gaskets, in which individual bars, rings or similar shapes of elastomeric material are applied to the core at critical points. These bars and strips are generally narrow, linear or band-shaped and are applied to the core by screen printing. These gaskets have the disadvantage that, due to the linear or strip-like overlays on the core, the gasket has only one position which provides optimum sealing. This position corresponds to the distribution pattern of the elastomeric strips. These gaskets can deform more in the regions of the elastomeric overlays and less in the other regions. Particular care must be taken to use the gasket in such a way that the regions capable of less deformation are not stressed beyond their capacity. The core of these gaskets must consequently be made sufficiently thick so that the inevitable physical variations in the surfaces to be sealed can be accommodated with sufficient safety margins.
During use, the core structure of these gaskets is subject to settlement, whereby the core becomes thinner. Such settlement can cause the gasket to lose contact with the surfaces to be sealed, leading to potential uncontrolled pressure loses and gasket failure. Another problem is that the core material may, depending on the load, be squeezed out from between the surfaces to be sealed, which also reduces the sealing capacity of the gasket.
Incompressible cores of metal have been used to manufacture gaskets. When metal cores have been used, elastomeric overlays are applied to the sheet metal. In these gaskets, although the core is sufficiently stable and durable, the elastomeric overlays must bear the entire contact pressure. Particularly in situations where dynamic loading is present, the elastomeric overlays are easily destroyed and no longer fulfill their sealing function.
German patent application OS No. 34 39 602 discloses a flat gasket for use as a cylinder-head gasket in an internal combustion engine where a separately fabricated fine-mesh net of elastomeric material is applied to a core of compressible or incompressible material in order to provide an improved surface seal. The production of the net-like elastomeric overlay, separate from the core, is difficult and expensive. Also, individual adaptation of the net structure to individual sealing conditions for a given gasket is not possible. Such variations in sealing conditions result from the machining of the surface to be sealed which results in roughness variations, machining grooves, machining inaccuracies, as well as variations in tolerances between the surfaces.